Which tool would be used to measure wind shear at an airfield?

Choosing the LLWAS as the correct tool for measuring wind shear at an airfield is accurate because LLWAS, or Low-Level Wind Shear Alert System, is specifically designed to detect wind shear conditions, which are rapid changes in wind speed and direction over a short distance. This system utilizes a network of anemometers to monitor wind conditions at various altitudes, providing crucial data that helps pilots understand and respond to potential wind shear hazards during takeoff and landing.

On the other hand, the other options serve different functions that are not directly related to measuring wind shear. The ILS, or Instrument Landing System, assists in guiding aircraft for a safe landing but does not provide wind shear information. DME, or Distance Measuring Equipment, helps pilots determine their distance from a navigational aid, while PAPI, or Precision Approach Path Indicator, provides visual guidance to ensure that an aircraft approaches the runway at the correct angle. None of these tools are designed to measure or alert pilots to wind shear conditions like LLWAS does.